The man who was handpicked by JK Rowling to illustrate a new series of Harry Potter books visited the University of Northampton this week – and revealed what it was like to work with the world’s most famous living fiction writer.

Northamptonshire’s Jim Kay, whom Rowling described as “modesty itself, completely unaware that he's a genius”, appeared at Avenue Campus to promote the latest fully illustrated edition of the Potter saga: Harry Potter and the Prisoner of Azkaban.

Recollecting the moment he received the call that he’d been chosen for the job, Jim said: “I was terrified, because it was such a big thing and I didn’t sleep properly for six months because the responsibility would suddenly hit me – you don’t want to make a mess of the world’s most popular children’s book and that feeling never really left me.

“In fact, every time there’s a book release I’m still terrified, still nervous, but that keeps me going, you’ve got to keep on your toes.”

Jim also spoke about his relationship with Rowling, who has sold in excess of 500 million books – a figure which puts her alongside the likes of Agatha Christie, Shakespeare and Enid Blyton in the top 10 of the most successful fiction writers.

“The one person you want to please, as an illustrator, is the author,” said Jim. “So far I’ve had some amazing letters from Jo, really lovely letters, and she writes beautifully, as you’d imagine.

“So far she likes it, and I couldn’t ask for more than that.”

Jim went on to offer advice for students on the University of Northampton’s Illustration course.

“There are far better draughtsmen than me, but it’s all about perseverance and sticking power,” said Jim.

“If someone says I can’t do something it motivates me. Early on in my career, there were loads of failures and they made me really push hard.

“So don’t be put off by criticism, just build on it and learn from it. It smarts at the time, but retrospectively that’s often the kick up the backside you need.”